Water storage effect on the marginal seal of resin-modified glass-ionomer restorations

The effect of storage in water on the marginal adaptation of glass-ionomer restorations placed in extracted human premolars and Teflon molds was studied. When the cavity preparations were filled with a glass ionomer and polished immediately after setting, a marginal gap of approximately 15 mu m was formed. In contrast, when polishing following storage in water the marginal gap was 0 to 2 mu m for the resin-modified and the conventional glass ionomers respectively. The bond strength of the glass ionomer to enamel and to dentin and the flexural strength of the glass ionomer increased after storage in water. Therefore the marginal seal of glass-ionomer restorations may not only be improved due to hygroscopic expansion during storage in water but also may exhibit greater bond strength.